Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are generated by performing a DC-DC, DC-AC, and/or AC-DC conversion by operating a switch loaded with an inductor or transformer. One class of such systems includes switched mode power supplies (SMPS). An SMPS is usually more efficient than other types of power conversion systems because power conversion is performed by controlled charging and discharging of the inductor or transformer and reduces energy lost due to power dissipation across resistive voltage drops.
An SMPS usually includes at least one switch and an inductor or transformer. Some specific topologies include buck converters, boost converters, and flyback converters, among others. A control circuit is commonly used to open and close the switch to charge and discharge the inductor. In some applications, the current supplied to the load and/or the voltage supplied to the load is controlled via a feedback loop.
In some power supply applications, a switched mode power supply may be operated in two different modes: a continuous conduction mode (CCM) and a discontinuous conduction mode (DCM). During CCM, the switch(es) may be operated to continually charge or discharge the inductor. During DCM, the switch(es) may be operated so as to limit the amount of negative current flowing in the inductor during each cycle in order to improve efficiency. In battery charging applications, CCM may be used during the middle of the charging cycle and DCM may be used near the end of a charge cycle. As the load voltage or battery charge nears the target or supply voltage, the power supply may be operated in DCM in order to reduce the charge removed from the load or battery by negative currents. Such approaches are common in charging applications for energy efficiency and to prevent battery damage.